I always imagine pieces of fantasy artwork as windows into another world. Given that, I find an artist’s signature that is very visible, even dominating, to be very jarring and disruptive when attempting to soak in a scene.
Don’t get me wrong, there’s no right way to do these things. Some people’s signatures are practically a work of art unto themselves. Others, are vivid stamps of ownership. That’s just not to my taste.
In most of my pieces I keep my signature subtle, using colors from within the image and only rarely placing them against strongly contrasting colors. There are some Magic pieces where the only way you would ever see the signature would be to hold the original painting; the signature is minutely different in color to its background.
And then there are the occasions where I make the signature part of the decor, or an integral part of the image.